Engraving a text string in Blender Internal Render
Create your lingot first. Add a text object and give it some thickness extruding it in the properties geometry tab.




Place the text where you need it and convert it to a mesh: Alt C and select Mesh from Curve/Meta/Surf/Text



Select the Lingot,  add a Boolean Modifier and select the Text as object and use difference as operation.


You can now move the text to another layer that is not part of your rendered layers.



If you have different text objects you can change them by selecting them in boolean modifier.